1. Knight: Chapter 15 Fluids & Elasticity ( Pressure in liquids, Measuring and using pressure, & Buoyancy)

2. Pressure in Liquids What is the pressure at a depth d?

3. Pressure in Liquids Absolute Pressure, Gauge Pressure, What is the pressure at a depth d?

4. Pressure in Liquids  Force per unit area that a liquid exerts on a submerged object  Depth dependent and NOT volume dependent i.e. Swim twice as deep, then twice as much weight of water above you produces twice as much pressure on you.  Acts equally in all directions i.e.: Your ears feel the same pressure under water regardless of your head’s orientation.  Independent of shape of container: Regardless of the shape of a container, pressure is the same at any particular depth.

5. Quiz Question 1 Water pressure provided by a water tower is greater if the tower 1. is taller. 2. holds more water. 3. Both 1. and 2. 4. None of the above.

6. Pressure in Liquids  A connected liquid in hydrostatic equilibrium rises to the same height in all open regions of the container.  The pressure is the same at all points on a horizontal line through a connected liquid in hydrostatic equilibrium.

7. Suppose we change p 0 to p 1 … What happens to the pressure in the fluid? Pressure in Liquids

8. Pascal’s Principle A change in pressure at one point in an incompressible fluid appears undiminished at all points in the fluid.

9. Solving Hydrostatic Problems

10. Manometers

12. Barometers

15. The Hydraulic lift How does F 2 relate to F 1 ?

16. The Hydraulic lift How does F 2 relate to F 1 ?

17. The Hydraulic lift Suppose we lift the car higher… How does d 2 relate to d 1 ?

18. The Hydraulic lift Suppose we lift the car higher… How does d 2 relate to d 1 ? Notice: The distance is divided by the same factor as that by which the force is multiplied. statement of energy conservation.

19. The hydraulic lift at a car repair shop is filled with oil. The car rests on a 25-cm-diameter piston. To lift the car, compressed air is used to push down on a 6.0-cm-diameter piston. What does the gauge read when a 1300 kg car is 2.0 m above the compressed-air piston? i.e. 15.7: Lifting a car

20. Buoyancy Q: Why do things feel lighter underwater (or even float)? Imagine a block in a fluid… h1h1 h2h2 F1F1 F2F2 h P1P1 P2P2

21. The buoyant force is equal to the weight of the fluid displaced. Buoyancy